Slide 10.1 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Object-Oriented Software Engineering WCB/McGraw-Hill, 2008 Stephen R. Schach

Slide 10.2 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. CHAPTER 10 THE REQUIREMENTS WORKFLOW

Slide 10.3 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Overview l Determining what the client needs l Overview of the requirements workflow l Understanding the domain l The business model l Initial requirements l Initial understanding of the domain: The MSG Foundation case study l Initial business model: The MSG Foundation case study

Slide 10.4 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Overview (contd) l Initial requirements: The MSG Foundation case study l Continuing the requirements workflow: The MSG Foundation case study l Revising the requirements: The MSG Foundation case study l The test workflow: The MSG Foundation case study l What are object-oriented requirements? l Rapid prototyping

Slide 10.5 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Overview (contd) l Human factors l Reusing the rapid prototype l CASE tools for the requirements workflow l Metrics for the requirements workflow l Challenges of the requirements workflow

Slide 10.6 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. The Aim of the Requirements Workflow l To answer the question: – What must the product be able to do? l Misconception – We must determine what the client wants l “I know you believe you understood what you think I said, but I am not sure you realize that what you heard is not what I meant!” l We must determine what the client needs

Slide 10.7 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Determining What the Client Needs l It is hard for a systems analyst to visualize a software product and its functionality – The problem is far worse for the client l A skilled systems analyst is needed to elicit the appropriate information from the client l The solution: – Obtain initial information from the client – Use this initial information as input to the Unified Process – Follow the steps of the Unified Process to determine the client’s real needs

Slide 10.8 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Overview of the Requirements Workflow l First, gain an understanding of the application domain (or domain, for short) – The specific environment in which the target product is to operate l Second, build a business model – Model the client’s business processes l Third, use the business model to determine the client’s requirements l Iterate the above steps

Slide 10.9 Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Definitions l Discovering the client’s requirements – Requirements elicitation (or requirements capture) – Methods include interviews and surveys l Refining and extending the initial requirements – Requirements analysis

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Understanding the Domain l Every member of the development team must become fully familiar with the application domain – Correct terminology is essential l Construct a glossary – A list of technical words used in the domain, and their meanings

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Business Model l A business model is a description of the business processes of an organization l The business model gives an understanding of the client’s business as a whole – This knowledge is essential for advising the client regarding computerization l The systems analyst needs to obtain a detailed understanding of the various business processes – Different techniques are used, primarily interviewing

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Interviewing l The requirements team meet with the client and users to extract all relevant information l There are two types of questions – Close-ended questions require a specific answer – Open-ended questions are posed to encourage the person being interviewed to speak out l There are two types of interviews – In a structured interview, specific preplanned questions are asked, frequently close-ended – In an unstructured interview, questions are posed in response to the answers received, frequently open-ended

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Interviewing (contd) l Interviewing is not easy – An interview that is too unstructured will not yield much relevant information – The interviewer must be fully familiar with the application domain – The interviewer must remain open-minded at all times l After the interview, the interviewer must prepare a written report – It is strongly advisable to give a copy of the report to the person who was interviewed

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Other Techniques l A questionnaire is useful when the opinions of hundreds of individuals need to be determined l Examination of business forms shows how the client currently does business l Direct observation of the employees while they perform their duties can be useful – Videotape cameras are a modern version of this technique – But, it can take a long time to analyze the tapes – Employees may view the cameras as an unwarranted invasion of privacy

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Use Cases l A use case models an interaction between the software product itself and the users of that software product (actors) l Example: Figure 10.1

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Use Cases (contd) l An actor is a member of the world outside the software product l It is usually easy to identify an actor – An actor is frequently a user of the software product l In general, an actor plays a role with regard to the software product. This role is – As a user; or – As an initiator; or – As someone who plays a critical part in the use case

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Use Cases (contd) l Conversely, one actor can be a participant in multiple use cases l Example: A Borrower may be an actor in – The Borrow Money use case; – The Pay Interest on Loan use case; and – The Repay Loan Principal use case l Also, the actor Borrower may stand for many thousands of bank customers

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Use Cases (contd) l Alternatively: – Actor Medical Staff with two specializations: Physician and Nurse Figure 10.2

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Initial Requirements l The initial requirements are based on the initial business model; then they are refined The requirements are dynamic — there are frequent changes l There are two categories of requirements – A functional requirement specifies an action that the software product must be able to perform » Often expressed in terms of inputs and outputs – A nonfunctional requirement specifies properties of the software product itself, such as » Platform constraints » Response times » Reliability

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Initial Requirements (contd) l Functional requirements are handled as part of the requirements and analysis workflows l Some nonfunctional requirements have to wait until the design workflow – The detailed information for some nonfunctional requirements is not available until the requirements and analysis workflows have been completed

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved What are Object-Oriented Requirements? l There is no such thing as “object-oriented requirements” – The requirements workflow has nothing to do with how the product is to be built l However, the approach presented in this chapter is – Model oriented, and therefore – Object oriented

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Rapid Prototyping l Hastily built (“rapid”) – Imperfections can be ignored l Exhibits only key functionality l Emphasis on only what the client sees – Error checking, file updating can be ignored l Aim: – To provide the client with an understanding of the product l A rapid prototype is built for change

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Human Factors l The client and intended users must interact with the user interface l Human-computer interface (HCI) – Menu, not command line – “Point and click” – Windows, icons, pull-down menus

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Human Factors (contd) l Human factors must be taken into account – Avoid a lengthy sequence of menus – Allow the expertise level of an interface to be modified – Uniformity of appearance is important – Advanced psychology vs. common sense? l Rapid prototype of the HCI of every product is obligatory

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Reusing the Rapid Prototype l Reusing a rapid prototype is essentially code-and- fix l Changes are made to a working product – Expensive l Maintenance is hard without specification and design documents l Real-time constraints are hard to meet

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Reusing the Rapid Prototype (contd) l One way to ensure that the rapid prototype is discarded – Implement it in a different language from that of the target product l Generated code can be reused l We can safely retain (parts of) a rapid prototype if – This is prearranged – Those parts pass SQA inspections – However, this is not “classical” rapid prototyping

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved CASE Tools for the Requirements Workflow l We need graphical tools for UML diagrams – To make it easy to change UML diagrams – The documentation is stored in the tool and therefore is always available l Such tools are sometimes hard to use l The diagrams may need considerable “tweaking” l Overall, the strengths outweigh the weaknesses

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. CASE Tools for the Requirements Workflow (contd) l Graphical CASE environments extended to support UML include – System Architect – Software through Pictures l Object-oriented CASE environments include – IBM Rational Rose – Together – ArgoUML (open source)

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Metrics for the Requirements Workflow l Volatility and speed of convergence are measures of how rapidly the client’s needs are determined l The number of changes made during subsequent phases l Changes initiated by the developers – Too many changes can mean the process is flawed l Changes initiated by the client – Moving target problem

Slide Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved Challenges of the Requirements Phase l Employees of the client organization often feel threatened by computerization l The requirements team members must be able to negotiate – The client’s needs may have to be scaled down l Key employees of the client organization may not have the time for essential in-depth discussions l Flexibility and objectivity are essential